Rotary engine.



PATENTED SEPT. 5, 1905 1a annn'rs-snnn'r .1

E. G. WARREN. ROTARY ENGINE.

APPLIGATIOH rI sn NOV. 29, 1901.

PATENTED SEPT. 5, 1905.

E. 0. WARREN. ROTARY ENGINE.

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ROTARY ENGINE.

APPLIOATION rum) NOV. 29, 1901.

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ROTARY ENGINE.

APPLICATION IILBD NOV. 29, 1901.

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PATENTED SEPT. 5, 1905.

E. 0. WARREN.

ROTARY ENGINE. APPLICATION FILED 1107.29, 1901.

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B. G. WARREN.

ROTARY ENGINE.

APPLICATION FILED NOV. 29, 1901.

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PATENTED SEPT. 5, 1905.

E. G. WARREN. ROTARY ENGINE.

PATENTED SEPT. 5, 1905.

E. G. WARREN.

ROTARY ENGINE.

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No. 798,848. PATENTED SEPT. 5, 1905.

E. G. WARREN.

ROTARY ENGINE.

APPLICATION FILED nov. 29. 1901.

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PATENTED SEPT. 5, 1905.

B. G, WARREN. ROTARY ENGINE.

APPLICATION rmm HOV. 2e. 1901.

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PATENTED SEPT. 5, 1905.

E. C. WARREN.

ROTARY ENGINE.

APPLIGATION FILED NOV. 29, 1901.

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% AM 0a N0- 798,848. PATENTED SEPT. 5, 1905. B. C. WARREN.

ROTARY ENGINE.

APPLICATION mum nov. 29. 1901.

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PATENTED SEPT. 5, 1905.

E. G. WARREN.

ROTARY ENGINE.

APPLICATION rmm xov. as, 1901.

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amnammuias wlsmmvou UNITED STATES PATENT OFFICE.

ElHVARD U. WARREN, OF Pl\ ()\"'ll)EN( l 1, RIIODE lhln'\Nl), AbblGNOR TO THE ROTARY ENGlNE COMPANY, A GORPORATIION OF DELAWARE.

ROTARY ENGINE.

Specification of Letters Patent.

Patented Sept. 5, 1905.

, Application filed November 29, 1901. Serial No. 84,073.

Be it known that I, EDWARD U. \Yanumr, a 1 fully set forth.

citizen of the United States, residing at Providence, county of Prevalence, and State of Rhode Island, have invented certain new and useful Improvements in Rotary Engines, of

range the rotary abutments in such manner as to shorten up or greatly reduce the length of certain of the steanrpassages; to provide an arrangement whereby the steam-leakage may be economically employed for effecting the desired or proper lubrication of the various parts; to aiford an arrangement whereby the lubricating-oil may be caused to flow between the moving or operative parts in such manner as to retard or hinder the leakage of the steam; to provide a construction whereby a plurality of pistons may be employed and whereby one piston may be brought partially within the other in such manner as to desirably and advantageously reduce the length of the engine; to provide a construction which will facilitate in assembling the various parts of which the engineis composed and which will also facilitate in taking the engine apart in case it may become desirable to repair or substitute new parts for broken or worn-out portions; to provide a form of reversing-valve mechanism by which the engine can be effectively and eiliciently reversed by neutralizing the high-pressure piston and admitting live steam directly to the low-pressure piston; to provide a construction and arrangement of the parts which will insure strength and rigidity, and to provide certain details and features of improvement tending to increase the general efticiency and serviceability of a rotary engine of this character.

To the foregoing and other useful ends my in the accompanying drawings, Figure 1 is a horizontal section taken centrally through a compound reversible rotary engine involving the principles of my invention. Fig. 2 is a vertical section on line 2 2 in Fig. 1. Fig. 3 is a vertical section on line 3 3 in Fig. 1. Fig. i is a transverse vertical section on line i 4: in Fig. 3. Fig. 5 is a similar transverse section on line 5 5 in Fig. 3. Fig. 6 is a front elevation of a rotary engine, as shown in Fig. 1. Fig. 7 is a transverse or cross-section on line T T in Fig. 1. Figs. 8, 9, and 10 are detail views illustrating the split horseshoe shaped rings which are employed in connection with the abutments for the low-pressure piston. Fig. 11 is a view of the rear end of the engine, showing the cylinder-head reremoved so as to expose the gearing which connects the abutment-shafts with the lowpressure piston. Fig. 12 is a detail section of the gear-ring which is applied to the highpressure piston and which meshes with the cogs or small gears on the high-pressure abutments. Fig. 13 is a longitudinal section through the high-pressure piston. Fig. 14: is a transverse section on line 1a 1a in Fig. 1. Figs. 15, 16, and 17 illustrate thesplithorseshoe-shaped rings which are employed in connection with the high-pressure abutments and which are similar to the split rings or plates shown in Figs. 8, 9, and 10. Fig. lb is a transverse section on line 18 18 in Fig. 1. Fig. 19 is a detail section through a portion of the cylinder-casing on line l9 19 in Fig. 18. Fig. 20 is a view showing the two pistons in section mounted on a shaft and removed from the engine. Fig. 21 is a view similar to Fig. 20, but showing the two pistons in elevation instead of in section. Fig. 22 is a perspective of my improved valve mechanism for reversing the engine. Fig. 23 is a detail elevation of one of the two bushings employed for inclosing the rotary reversing valves. Fig. 2a is a detail elevation of one of the said rotary reversingvalves. Figs. 25 and 26 are cross-sections of the bushing shown in Fig. 23. Fig. 27 is a section through the main portion of the engine-casing and also through the reversing-valves, the sections being taken on the irregular line 27 9.7 in Fig. 4. Figs. 28 and 2-9 are detail views more or less diagrammatic in character and showing the manner in which one of the reversing-valves and the adjacent ports or cored passages cooperate to reverse the engine.

The rotary engine thus illustrated is compound or steam-expanding in character and comprises the main cylinder-casing 1, the lowpressure-cylinder head 2', the high-pressurecylinder head 3, the casing and heads thus provided and arranged being adapted to inclose the high and low pressure pistonstand 5. These pistons are, it will be observed, cylindric in form, and the high-pressure piston is preferably provided with a ring-gear 6, while the low-pressure piston is provided with a similar ring-gear 7. It will be observed that the said high-pressure piston is relatively ton is preferably secured to the latters outer or rear end.

ably reduced. arranged, preferably, at each side of the low- Both pistons are secured in any suitable manner to the main shaft 24. This main shaft is preferably tapered at its forward end to receive the high-pressure piston and is also preferably provided at this end with a reduced threaded portion adapted to receive a nut for clamping or securing the high-pressure piston in place.

The main casing, it will be observed, is so formed or constructed as to provide a cylindric or annular chamber for the low-pressure piston and also a smaller chamber adapted to receive the cylindric high-pressure piston. This is shown in Fig. 7, wherein it will be seen that the chamber or the portion of the casing which incloses the high-pressure piston extends within the chamber which incloses the low-pressure piston. In this way the pistons are brought one within the other, and the length of the engine is thereby consider- The rotary abutments 8 are pressure piston and are preferably and desirably provided with gears 9, adapted to engage the ring-gear 7 on the said low-pressure piston. The high-pressure abutments 10 are preferably similar to the low-pressure abutments and are located substantially above and below the high-pressure piston. As shown in Fig. l, for example, these high-pressure abutments are arranged at an angle with respect to the low-pressure abutments, the upper At the rear of the engine the shaft 24 is preferably and desirably supported in a suitable bearing composed, preferably, of the outboard bearing 12, the outboard-bearing cap 13, bolted or secured thereto, and the thrustbearings and half-couplings 14 and 15. It will also be observed that this hearing structure includes a half-coupling 16. Leakage through the shaft-bearing as constructed is preferably prevented by a stufling-box composed of the stufling-box gland 17 and the gland-collar 18. This gland-collar is preferably backed by the bushing 19 and 20, which forms the main bearing for the shaft. Thus constructed the shaft bearing two pistons is suitably mounted for rotation and held against end play by the thrust-bearing composed of the outboard bearing and the adjacent parts arranged outside of the stuffing-box. With this arrangement the pistons can be arranged to run free and have their end parts or surfaces stand clear of the inner surface of the casing.

Bushings 21 are preferably and desirably provided for the low-pressure-abutment spindles and similar bushings 22 are provided for the high pressure piston spindles. These high-pressure-abutment spindles are also provided with inner bushings 23. A nut 25 is adapted to screw onto the forward end of the main shaft and, as stated, is for the purpose of clamping the high-pressure piston firmly upon the main shaft. A similar nut 26 is screwed onto the rear end of the said shaft and is designed to clamp or hold the thrustbearing and halfcoupling l4 tightly upon the tapering portion of said shaft. With this arrangement the flanged inner end of-the thrustbearing is held firmly between the outboard bearing 12 and the thrust bearing cap or plate 13. The half-coupling 16 can be employed for connecting the engine-shaft with the machinery or devices which are to be driven by the engine.

As will be observed, each low pressure abutment is preferably cylindric in form and mounted upon a spindle 27. As stated, these abutment-spindles are supported for rotation in the bushings 21, arranged at the opposite ends of the abutments. The high-pressure abutments are likewise preferably mounted upon spindles 28, and these spindles, as previously explained, are supported for rotation in the bushings 22 and 23. These spindles for the high-pressure abutments preferably extend through at each end, and the highpressure-cylinder head is preferably provided with caps 29, adapted to cover the outer ends of the bushings 22 and the said spindles 28. It will also be observed that these spindles are preferably hollow-that is to say, that they are formed with longitudinal bores opening at each end into the bushings 22 23. The low-pressure-abutment spindles are also preferably provided with longitudinal passages, and these passages through the abutmentspindles, in connection with the oil ducts through the main shaft, (see particularly Fig. 1,) afford suitable channels whereby the leakage over the flanges of the high-pressure piston and thence through the different parts may be utilized for the purpose of carrying the lubricating-ml between the parts which move relatively to each other. Preferably, as will be observed, no mechanical packing is employed, and this being the case there is necessarily some leakage. However, as stated, the leakage from the high-pressure piston is conducted through suitable channels and forced to escape into the low-pressure cylinder in such manner as to carry with it a suitable quantity of lubricating-oil. In this way I not only take advantage of the steam-leakage for the purpose of insuring proper lubrication of all the operative parts, but I also apply the oil in such manner that it tends to retard or hinder such leakage, thereby obviating the necessity of providing packing.

Preferably the low-pressure-abutmentspindles project through at each end---that is to say, are of a length to extend through the casing -and these exposed end portions are preferablycovered by threaded caps 30, which are similar to the caps 29. \Vith this arrangement ready and convenient access may be had to the abutment-bearings either for the purpose of cleaning or additional lubrication.

As will be hereinafter explained, theenginecasing is provided with suitable ports or passages for conducting the steam first to the high-pressure piston and for then exhausting the steam from this piston directly into the chamber containing the low-pressure piston. In this way, as previously stated, the engine is of the compound or steam-expanding type, and in order that the engine may be reversed at will I provide a pair of reversing-valves 31 and 1:31. recessed and otherwise adapted to cooperate with said ports or passages in controlling the ad mission and exhaust of the steam to and from the pistons. These valves are retatable for the purpose of permitting the order of admission and exhaust to be reversedthat is to say, for the purpose of permitting the admission of steam to be reversed in such manner as to reverse the rotation of the piston-shaft. As an effective and efficient method of reversing the engine said valves and ports or passages are preferably of such character as to render the higlrpressure piston neutral when the engine reversed. \Vhen the valves are in position to drive the engine forward or in a go-ahead direction, the steam is, as explainel, first admitted to the high-pressure piston and is then exhausted from the chamber containing this piston to the chamber containing the low-pressure piston. hen it passes from the high-pressure piston to the low-pressure piston, the steam expands, and in this way the efhclency of the englne is 1ncreased as a result of using the steam expansively in the well-known manner. The said rotary valves are preferably mounted in bushings 32 and 32, which are ported or apertured to afford communication through the valve from one passage to the other. Referring particularly to Fig. 3 and also to Fig. 22, it will be seen that the outer portion of each valve-bushing is preferably provided with a cap 33. Located between the outer ends of these valves is the oil-fitting 34, provided externally with an acorn-nut 35, which affords a simple and efi'ectivedevice for introducing the oil into the duct or channel extending longitudinally through the forward portion of the main piston-shaft. A pipe or other suitable conductor can be employed for conducting oil to this fitting, and, as-stated, the pressure of the steam leaking from the flanges of the high-pressu re piston will carry the oil forward into the piston-shaft passage and force it into the bearings provided by the bushings 19 and 21. The outer end portions of the reversingvalves thus arranged at opposite sides of the oil-fitting can be connected for simultaneous adjustment in any suitable manner. For example, this sinmltaneous adjustment can be accomplished by providing a horizontally-disposed link 36 and a vertically-disposed link 37. This horizontally-disposed link can be arranged to connect a pivotally-moun ted bellerank 38 with the crank-arm 39, the latter being secured to the outer end of the valve 31. The other arm of this bell-crank 38 is connected with the reversing-lever at) by means of the aforesaid vertically-disposed link 37. This reversing-lever, it will be observed, is secured to the outer end of the reversingvalve 31. As shown in Fig. (3, for example, and also in Fig. 22, the valve mechanism thus constructed is shown in the go-ahcad position, the lever being depressed. ln order to reverse the engine, it is only necessary to lift the lever 40, so as to partially rotate the said rotary valves, this rotary :uljustment operating to change or alter the course of the steam through the passages in such manner as to admit live steam directly to the low-pressure piston. As stated, a reversal of the engine also involves a neutralization of the highpressure piston by admitting steam through both the admission and exhaust ports of the latter. In this way, as previously stated and as will hereinafter more fully appear, the engine when running backward is running under high pressure in what is normally the lowpressure cylinder and with a neutralized or idle high pressure piston. mechanism, it will be observed, is advantageously and conveniently arranged at the forward end of the engine and outside of the thin metallic cap or head-cover 41, which is shown as inclosing the cylinder-head for the high-pressure cylinder and piston.

As a matter of mechanical construction or The reversing-valve detail the main portion of the engine-casing can be inclosed by a lagging 42. This lagging can be held in place by lagging-strips 43. It will also be observed that in each case the rotary abutment and its cog or gear are formed integral and connected by a sort of hub portion, leaving an annular groove or space between them. Into these annular spaces or grooves are seated the abutmentplates or horseshoe-shaped rings 44, the latter for the low-pressure abutments, and similar plates or horseshoe-shaped rings 45 for the high-pressure abutments. Referring to Figs. 7 to 10, inclusive, it will be seen that these abutmentplates or horseshoe-shaped rings for the low-pressure abutments are preferably split, so as to permit them to be properly adjusted on the hub portion connecting the abutment with its cog or gear. It will also be seen that the concave edge portion with which each ring or plate is provided renders it, as stated, substantially horseshoeshaped in form and adapts it for contact or engagement with the annular peripheral flange on the rear end of the lo\ pressur'e piston.

This flange on the rear end of the low-pressure piston is fitted in the bore of the lowpressure cylinder, and these horseshoe-shaped rings or plates 4A form a tight joint and practically form continuations of the piston-flange.

Referring to Figs. 14 to 17, inclusive. it will be seen that the plates or rings 45 for the highpressure abutments are similar in form to those just described in connection with the low-pressure abutments. These horseshoeshaped rings or plates for the high-pressure abutments are also preferably split or made in two sections in view of the fact that the .abutments and their cogs or gears are, as explained, made integral. With this integral formation of the gears and abutments the said horseshoe-shaped rings or plates are necessarily splitor made in sections in order that they may be adjusted into place on the hub portions which connect their abutments with their respective gears or,cogs.

Referring to Figs. 20 and 21, it will be seen that each piston is, as stated, cylindric in form and that these pistons are provided at their opposite ends with peripheral flanges which fit the bore portions of the cylinder-casing. Each piston is preferably provided with three piston projections or vanes arranged between the said flanges. For example, the low-pressure piston is provided with the three piston projections or vanes 6, arranged at regular intervals around the circumference of the piston, and the smaller or high-pressure piston is provided with a similar trio of piston projections or vanes 17. The low-pressure abutments are provided peripherally with notches 48, and the high-pressure abutments are provided in a similar way with notches L9. WVith this arrangement the abutments make three rotations while the pistons are making one,

steam in these balancing chambers or recesses operates to balance the pressure exerted upon the abutments by the steam in the pistonchambers. In this way the abutments are perfectly balanced and mounted to turn freely and without any undue friction.

As previously stated, and as shown, for example, in Figs. 1, 20, and 21, it will be seen that the high-pressure piston extends practically within the low-pressure piston, the relative proportion being such as to readily permit this arrangement. In this way the two pistons are brought together in such manner as to greatly reduce the length of the engin e, and it will also be seen that this arrangement tends to shorten the length of the passages extending between the two cylinders. It will be readily understood that it is desirable to have the passages through which the steam is exhausted from the high-pressure cylinder to the low-pressure cylinder as short as possible. This I accomplish by the arrangement of the pistons and also by the aforesaid arrangement of the high-pressure abutments.

The relative formation of the pistons and the casing is such as to provide space or clearance at the ends of the pistons, so as to reduce to a minimum the contact necessary to provide tight joints between the pistons and the casing. IVith this arrangement the end walls of the cylinder-chambers are practically formed by the peripheral flanges on the pistons. As previously explained, the thrustbearing is particularly adapted for preventing end play on the part of the pistons, and is therefore of such character as to be readily adjustable for the purpose of properly adjusting the pistons within their respective cylinder-chambers. This construction is designed to permit high speed on the part of the engine in order to secure high efliciency. The engine is therefore, as stated, preferably constructed without packing of any sort, and with the steam-pressure balanced on all of the rotary parts in such manner as to reduce friction and uneven wearing to a minimum. In other words, there is no binding or rubbing between the parts, and the steam-pressure is so balanced as to permit the engine to run smoothly and at great speed. I

The operation of the rotary engine ,thus constructed is as follows: Referring more particularly to Figs. 2 and 18, steam is admitted from the pipe 50 to the annular steam- IOf space 51 surrounding the high-pressure chamber. From this annular steam-space steam is admitted directly to the high-pressure piston through the ports and 53. The admission of steam to the high-pressure cylinder in this manner operates to rotate the high-pressure piston in the direction indicated by the arrow, it being understood that pressure is exerted between the cylindric rotary abutments and the vanes or projections on the outer surface of the pistons. The exhaust then takes place from the high-pressure-piston chamber by way of the ports 54: and 55,

the steam passing through the openings 56 and j 57 in the valve-bushings, and thence through the recesses 58 and 59 in the cylindric rotary valves, thence through the ports 60 and (51 in the valve-bushings, and finally through the ports or passages 62 and 63 in the cylindric casing and into the chamber containing the low-pressure piston. Tlms the exhaust is conducted from the high-pressure piston to the chamber containing the low-pressure piston,

and the steam thus operating expansively? drives the low-pressure piston in the same direction as the live steam operates to drive the high-pressure piston. The exhaust from the low-pressure-piston chamber then takes place through the ports or openings 64 and 435, which open into the passages 66 and 67, extending around the lO\V-1)l0SSUl'(. chamber. From these relatively long passages tit and (37 the exhaust passes through the ports or slots 68 and 69 in the valve-bushings, thence through the recesses TO and 71 in the cylindric rotary valves, then through the ports or slots '72 and T3 in the valve-bushings, and finally into the exhaust-passages 7 t and 75, which communicate with the ultimate exhaust-opening T6. .In this way the live steam is, as explained, conducted first to the high-pressure chamber, where it exerts pressure between the highpressure piston projections and the highpressure abutments, and where it thereby acts to rotatively drive the pistons in the direction indicated by the arrow. The exhauststeam from the high-pressure-piston chamber then passes through the reversing-valves and enters the low-pressure chamber, where itexi l l l pands between the low-pressure abutments and the pro ections on the low-pressure plsi ton, and where it thereby further contributes an advantageous arrangement, as it avoids the necessity of having the steam till the abutment-recesses before exerting the requisite pressure on the piston-vanes. In other words, the steam when admitted acts instantaneously on the piston to drive it in the desired direction. As previously explained, the absence of any packing in the engine makes it possible to utilize the leakage around and over the pistons for forcing or carrying the lubricating-oil between the relatively moving parts,

and in this way the constantand even flow of steam through the passages and through the clearance-spaces operates to keep the engine thoroughly lubricated. It will also be seen, as previously stated. that the [low is of such character as to carry the oil into recesses where it may to some extent accumulate, and thereby tend to retard or hinder the leakage of the steam. in this way and by running the engine at high speed a high el'liciency is secured and the loss from leakage reduced to a minimum. As previously explained, the engine is preferably reversiole in character, and when reversed the high-pressure piston is preferably neutralthatis to say, the steam is admitted to the high -pressure chamber through all four of the ports. so as to exert an equal pressure on both sides of the piston vanes or projections. \Vhile the high-pressure piston is thus rendered neutral, live steam is permitted to enter directly into the lowpressure-piston chamber, thereby converting the piston that is normally a low-pressu re piston into a high-pressure piston. This is an effective and advantageous method of operation and permits theengine to run backward in an effective manner even though the steam is not employed in this case expansively. By reversing the engine in this manner the construction of the reversing-valves and the system of ports or passages can be greatly improved and simplified in character. To reverse the engine in this manner, it is, as previously explained, only necessary to raise or lift the lever it), so as to partially rotate the rotary reversing-valves, and thereby change the order of admission and exhaust. hen the valves are rotated by lifting the lever t0, the live steam is not only permittedto enter the high-pressure piston through the normal admissionports 52 and 52 but also by way of the normal exhaust-ports 5i and 55, it beingobserved that when the valves are reversed the passages 77 and 78, leading from the annular chamber 51, are thrown into communication with the exhaust-passages 5i and by reason of the relatively long recesses 70 and 71 being adjusted so as to connect the ports of slots 56 and 57 in the valve-bushings with the slots or openings 68 and 6%), which latter are also provided in the said valve-bushings. Thus when the valves are reversed live steam passes from the annular chamber 51 into the ducts or passages 77 and Ts, thence through the ports or openings 7%) and Si) in the valve-bushings, then through the said long recesses in the valves, then through the ports or openings 56 and 57 in the valve-lmshings, and linally through the exhaust-passages 5t and into the highpressure-piston chamber. In this way when interior of the relatively large piston, rotary abutments for said pistons. the rotary abutments of the small piston extending also within the interior of the relatively large piston, and a suitably-ported cylinder-easing for inclosing said pistons and abutments, substantially as (.lescribed.

A compound rotary engine comprising a 5 relatively large and a relatively small piston mounted upon a common shaft, the latter extending within the former, rotary abutments associated respectively with said relatively small and large pistons, gearing for connecting said pistons with said abutments, and a suitably-ported casing for inclosing said abutments, gearing and pistons, the steam being exhausted from the relatively small piston into the chamber containing the relatively large piston, substantially as described.

a. A compound rotary engine comprisinga plurality of cylindric pistons mounted upon a common shaft and extending one within the other, a suitably-ported c; sing inclosing said pistons and having clearance-space between its interior and the ends of the pistons, a tln'ust-bearing for said shaft adapted to prevent end play on the part of said pistons, rotary abutments for said pistons, and a threepart ported casing inclosing said pistons and supporting said thrust-bearing, a stuffing-box being interposed between said tln'ust-bearing and the interior of the engine, substantially as described.

T. A compound rotary engine comprising a relatively large piston mounted upon a pistonshaft, a relatively small piston mounted upon the same shaft, a ported cylinder-casing inclosing said pistons, there being clearancespace between theends of the pistons and the inner surfaces of the cylinder-casing, and a thrust-bearing arranged outside of the cylinder-casing and adapted to prevent end play on the part of said shaft, substantially as described.

A compound rotary engine comprising a rotary piston with periplieral vanes mounted upon a shaft, a three-part cylinder-casing inclosing said piston and provided with suitable ports or passages and with a clearancespace at the end of the piston, and a thrustbearing supported by the casing but outside of it, said tln'ust-bearing being adapted to prevent end play on the part of said shaft, substantially as described.

9. In a rotary engine,a piston mounted upon a shaft, a cylinder-casing inclosing said piston and having clearance between its inner surfaces and the ends of said piston, a shoulder upon said piston exposed to the internal pressure of the engine, and a thrust-bearing exterior to said casing, opposing movement of the shaft in the direction in which it is impelled by said internal pressure, substantially 3 as described.

it). A compound rotary engine comprising l relatively large and small pistons mounted in common upon a rotary shaft, rotary abutments for said pistons, gearing between said pistons and said almtments, a ported casing inclosing said pistons and abutments and also the gearing and having clearance between its l inner surface and the ends of the piston and i also between its inner surface and the said gearing, a suitable thrust-Waring exterior to said casing for preventing end play on the part of said shaft, and a stutling-box interposed between said thrust-bearing and the larger of said pistons, substantially as described.

11. A compound rotaryenginecomprisinga plurality of cylindric pistons extending one within the other and mounted upon a common shaft, :1 ported cylimler-casing for inc-losing said pistons, clearance-s1)ace between the ends of the pistons and the inner surface of the cyliruler-casing, and a suitable tln-ustbearing applied to the projecting end portion of said shaft and adapted to prevent end play on the part of said pistons, substantially as described.

12. A compound rotary engine comprisinga 1.)lurality of cylindric rotary pistons axially alined and extending one within the other, a shaft common to all of said pistons, a (.rylimlercasing inc-losing said pistons and one end of said shaft, there being clearance-space with reference to the meeting surfaces of the pis tons and the casing, and a tln'ust-bearing arranged adjacent to the larger of said pistons and applied to the projecting end portion of said shaft, so as to prevent end play on the part of said pistons within the casing, substantially as described.

13. A compound rotary engine comprising relatively large and small pistons axially alined and connected to rotate in unison, a suitable cylinder-casing for inclosing said pistons, said casing being suitably ported and provided with clearailce-spaces with respect to the pistons, and a tln'ust-bearing exterior to said casing havingsuitable coimection with said pistons and adapted to prevent end play on the part of the latter, substantially as described.

H. A compound rotary engine comprising a plurality of pistons mounted upon a common shaft, said shaft being provided with longitudinally and transversely extending oilducts, rotary abutments for said pistons, ringgears applied to the eudsof said pistons, cogs or pinions for connecting said abutments with said ring-gears, a cyliuder-casing inclosing said pistons, abutmcnts and gearing and having clearance-spaces with respect to the same, means for introd ucing oil into the longitudinal oil-duct in said shaft, the steam-leakage around the ends of the pistons carrying the oil through said passages in the piston-sha ft, and bearings for said shaft also lubricated by the oil thus [carried through by the steam-lealmge, the clearance-spaces and passages thus provided ITO 

